The Chinese Patent Application ZL 02114190.8 discloses 1-(substituted phenyl)-5-methyl-2-(1H)-pyridone compounds, wherein one of the compounds is FFD when n is 1, R is F and the R substituent is at the meta-position of the phenyl group. It also discloses the method for preparing 1-(substituted phenyl)-5-methyl-2-(1H)-pyridone compounds, but it does not disclose crystallization and purification methods for FFD. According to the method disclosed in the Chinese patent application, highly pure crystalline FFD cannot be obtained.
A cell experiment testing the effect of FFD on anti-fibrosis of renal interstitial cell is disclosed in the Journal of Central South University (Medical Sciences), 2004, vol. 29 (2), the result shows that FFD has a good effect on anti-fibrosis.
It is disclosed in the CN 1846699A and US20070203203 that FFD is useful for preventing and treating tissue and organ fibrosis of animal and human.
To date, there is no report about preparation of the crystalline FFD.
Methods for crystallizing organic compounds have been reported in the following documents: J. A. Landgrebe, Theory and Practice in the Organic Laboratory, 2nd Edition, pp. 43-51, published by D.C. Health and Co., Lexington (1977); and A. S. Myerson, Handbook of Industrial Crystallization, pp. 1-101, published by Butterworth Heinemann, Stoneham (1933).